1. Field of the Invention
The invention pertains to a control valve unit for an hydraulic elevator that does not require adjustment elements.
2. Description of Background Art
Such control valve units are used for influencing the flow of hydraulic oil between a pump or a tank, respectively, and a drive cylinder for the direct or indirect drive of an elevator cabin.
A control valve unit is known from U.S. Pat. No. 5,040,639. This control valve unit includes three pilot control valves as well as a return valve in which the opening status is monitored using a position indicator. In addition also still some adjustment elements exist beside fixed chokes.
From EP-A2-0 964 163 a similar control valve unit is known which is of a substantially more complex construction and which beside four main control valves and three pilot valves includes a series of mechanical adjustment elements.
The invention is based on the object of creating a control valve unit which is of simple construction and can do without adjustment elements. This results in low manufacturing costs and during installation time-consuming adjustments are not required.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.